Non-Contact Wet-Process Cell Confining Liquid to a Region of a Solid Surface by Differential Pressure

ABSTRACT

An open-bottomed reactor cell for wet processing of substrates can be configured to confine a process liquid to an area under the cell (processing the “internal site”), or alternatively to exclude the process liquid from most of the area under the cell (processing the “external site”) without physical contact between the cell and substrate. A slight underpressure or overpressure maintained inside the main cavity of the cell causes the liquid to form a meniscus in the narrow gap between the cell and substrate rather than flowing outside the desired process area. An area under a peripheral channel outside the main cavity of the cell is shared by both the internal site and the external side, allowing the entire substrate to be processed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Prov. Pat. App. No. 61/780,128,filed 13 Mar. 2013, which is entirely incorporated by reference hereinfor all purposes.

BACKGROUND

Related fields include combinatorial methods for device processdevelopment; in particular, combinatorial methods of developing andoptimizing wet processes and the formulations used in those processes.

A variety of electronic, optical, or micro-mechanical devices arefabricated by forming many small components on a common larger substrate(e.g., a semiconductor wafer or a sheet of glass, polymer, or carbon).“Wet” processes, involving the application of liquid to the substrate,may be used in many phases of fabrication: cleaning, etching, polishing,texturing, passivation and other surface reactions, and film-depositionmethods such as plating, dip-coating, and spin-coating.

Often the fabrication of a particular device involves both wet processesand “dry” (no-liquid) processes such as treatments with gas, plasma,solid particulates, or electrical and magnetic fields. The performanceof these devices is often highly sensitive to contamination. Performingas many of the processes as possible in the same controlled environment(e.g., the same process chamber or sealed group of chambers) minimizesthe risk of exposure. The risk of contamination exposure is also reducedby reducing the need for chamber-cleaning operations that admit ambientatmosphere to the chamber; confining both dry and wet process substancesto the substrate surface, where possible, is helpful.

Since most substrates are flat, the confinement of liquid can bechallenging. Often the liquid is dispensed from a cell, or reactor,inside the chamber. An open end of the cell may seal to the substrate bytouching it. However, unwanted particle deposition, abrasion, and otherforms of damage may result from the contact. This may be tolerable ifthe affected area does not include any device features; for example, theextreme outer periphery of a substrate may be left unprocessed tofacilitate robotic handling or for other reasons. However, somefabrication methods call for isolated processing of one or more regionsof the substrate that may be adjacent to other regions where devices arefabricated.

One example of a requirement for isolated processing of regions on asubstrate is high-productivity combinatorial (HPC) processing. As partof the discovery, optimization and qualification of each unit process,it is desirable to rapidly and efficiently test different i) materials,ii) unit-process conditions, iii) sequences and integrations ofunit-process modules in a processing tool, iv) sequences of processingtools in different process-integration flows, and (v) combinationsthereof. Results can be acquired faster and at lower cost if each set ofvariables tested does not consume an entire substrate; i.e., if multiplematerials, process conditions, sequences, integration flows, orcombinations can be tested on isolated sites of the same substrate. HPCprocessing techniques have been successfully adapted to both dry and wetchemical processing.

Known non-contact approaches to site-isolated or substrate-confined wetprocessing include suspending the substrate with the process surfacefacing downward and sending the liquid upward to the surface withatomizers or impellers. Other non-contact approaches include dispensinga barrier liquid or gas around the periphery of the cell; the pressureof the barrier liquid or gas acts to confine the process liquid to thedesired area of the substrate. The mechanisms for these approaches arecomplex and costly. Some require high-quality consumables that also addcost. Some approaches also leave undesired gaps between processed sites,or may require moving the reactor cell or the substrate to producecontiguous or overlapping processed sites.

Therefore, the industry would benefit from simple, robust non-contacttechniques for confining wet-process liquids to isolated sites on asubstrate. Additional benefits would result from an ability to processcontiguous or overlapping sites without needing to translate the reactorcell(s) or the substrate.

SUMMARY

The following summary presents some concepts in a simplified form as anintroduction to the detailed description that follows. It does notnecessarily identify key or critical elements and is not intended toreflect a scope of invention.

The body of a reactor cell for processing an isolated site on asubstrate has a peripheral channel around its main cavity. At least fourcavity ports (CP1, CP2, CP3, CP4) connect the outside of the body to themain cavity, and at least one peripheral port (PP) connects the outsideof the body to the peripheral channel. The manipulation of fluid(meaning either liquid or gas) communication through the ports allowsprocess liquid to be confined to either (1) an area of the substrateinside a circle defined by the outer border of the peripheral channel(the “internal site”), or (2) an area of the substrate outside a circledefined by the inner border of the peripheral channel (the “externalsite”). If both areas are processed in sequence, there is an overlapregion, defined by the inner and outer borders of the peripheralchannel, which is processed twice. For example, if the opening of theperipheral channel facing the substrate is circular, the twice-processedoverlap region is annular. In operation, the reactor cell is placed justslightly above the substrate surface, never touching. The gap height ischosen in a range where surface tension dominates the process liquid'swetting behavior (e.g., about 0.25 mm).

To process the internal site, CP1 is connected to PP; CP2 is connectedto a process-liquid source; CP3 is connected to a controllable exhaust(e.g., a vacuum pump configured to evacuate the main cavity); and CP4 isconnected to a controllable gas source. As liquid is introduced throughCP2, gas inflow through CP4 and gas outflow through CP3 are balanced tomaintain a constant underpressure, compared to the ambient chamberpressure outside the reactor cell, of about −25 mm H₂O. For example, CP3may be connected to an exhaust via a mass flow controller and CP4 mayhave an orifice connected to the chamber ambient atmosphere. The orificecontrols the flow impedance, the mass flow controller controls the flowrate and the two controls together maintain the desired underpressure inthe reactor cell. The liquid is allowed to fill the cavity and channelabove the gap; e.g., to a height of about 6 mm above the substrate.Meniscus effects, coupled with the pressure differential, cause theprocess liquid to wet up the peripheral channel rather than spreadingacross the substrate outside the cell.

To process the external site, PP is opened to the chamber ambient; CP1and CP2 are sealed; gas flows controllably in through CP3 and outthrough CP4. For example, CP3 may be connected to a pressure source(e.g., a container of pressurized gas or a gas compressor) and CP4 mayhave an orifice connected to the chamber ambient atmosphere. The controlof flow impedance by the orifice and the control of flow by the massflow controller together maintain the desired overpressure in thereactor cell. Process liquid is introduced outside the cell while thegas inflow and outflow inside the main cavity is controlled to produce aslight overpressure (˜+25 mm H₂O) compared to the chamber ambient. Theliquid is allowed to fill the peripheral channel above the gap; e.g., toa height of about 6 mm above the substrate. Meniscus effects, coupledwith the pressure differential, cause the process liquid to wet up theperipheral channel rather than spreading across the substrate into thearea under the main cavity.

In both cases, the process liquid wetting up into the peripheral channelcovers the area of substrate directly under the peripheral channel. Thusthis area is common to the external site and the internal site, and willbe processed twice as a result of sequential processing of the externaland internal sites.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings may illustrate examples of concepts,embodiments, or results. They do not define or limit the scope ofinvention. They are not drawn to any absolute or relative scale. In somecases, identical or similar reference numbers may be used for identicalor similar features in multiple drawings.

FIG. 1 is a schematic diagram of device development using primary,secondary, and tertiary screening methods that include HPC processingand may also include conventional processing.

FIG. 2 is a simplified schematic diagram illustrating a generalmethodology for combinatorial process sequence integration that includessite-isolated processing, conventional processing, or both.

FIGS. 3A and 3B are two conceptual views of a combinatorially-processedsubstrate.

FIG. 4 is a schematic diagram of one type of generic combinatorial wetprocessing system used to investigate processes involving liquids.

FIGS. 5A, 5B, and 5C are various schematic views of an example of ano-contact reactor cell body.

FIGS. 6A and 6B are schematic cross-sections of a no-contact reactorcell with a controllable orifice processing an internal site and anexternal site of a substrate.

FIGS. 7A and 7B are schematic cross-sections of a no-contact reactorcell with controllable gas inlet and exhaust processing an internal siteand an external site of a substrate.

FIG. 8 is a flowchart of a method for processing an internal site on asubstrate.

FIG. 9 is a flowchart of a method for processing an external site on asubstrate.

FIGS. 10A-10D are conceptual views of substrates with sequentiallyprocessed internal and external sites.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, methods for evaluating processingconditions and wet chemicals are illustrated using a simple planarstructure. The description and teachings can be readily applied to anysimple or complex testing methodology.

Unless the text or context clearly dictates otherwise: (1) By default,singular articles “a,” “an,” and “the” (or the absence of an article)may encompass plural variations; for example, “a layer” may mean “one ormore layers.” (2) “Or” in a list of multiple items means that any, all,or any combination of less than all the items in the list may be used inthe invention. (3) Where a range of values is provided, each interveningvalue is encompassed within the invention. (4) “About” or“approximately” contemplates up to 10% variation; “substantially”contemplates up to 5% variation. (5) “Fluid” may be either liquid orgas. (6) A “port” is an opening for fluid communication betweenotherwise separate spaces. (7) “Wet” and “wick” describe spreading ofliquid on a surface due to adhesion. (8) “Process liquid” may includecolloids or suspensions containing solid particles and capable offlowing (e.g., slurries).

HPC generally varies materials, unit processes, or process sequences(collectively, “candidates”) across multiple regions on a substrate. Theresults of the variations can be characterized to determine whichcandidates merit further evaluation or may be the most suitable forproduction or high-volume manufacturing. Systems and methods for HPCprocessing are described in U.S. Pat. Nos. 7,544,574, 7,824,935,7,871,928, 7,902,063, 7,947,531, and 8,084,400, and also in US PublishedPat. Apps. 2007/0267631, 2007/0202614, and 2007/0202610. All of theseare incorporated by reference herein for all purposes.

FIG. 1 is a schematic diagram of device development using primary,secondary, and tertiary screening methods that include HPC processingand may also include conventional processing. The diagram 100illustrates how the selection of a subset of the most promisingcandidates at each stage decreases the relative number of combinatorialprocesses that need to be run in the next stage. Generally, a largenumber of processes are performed during a primary screening stage.Based on the primary-screening results, a subset of promising candidatesis selected and subjected to a secondary screening stage. Based on thesecondary-screening results, a smaller subset of promising candidates isselected and subjected to a tertiary screening stage, and so on. Inaddition, feedback from later stages to earlier stages can be used torefine the success criteria and provide better screening results.

For example, thousands of materials may be evaluated during a materialsdiscovery stage 102, a primary screening stage. Techniques for thisstage may include, e.g., dividing substrates into coupons and depositingmaterials on each of the coupons. Materials, deposition processes, orboth may vary from coupon to coupon. The processed coupons are thenevaluated using various metrology tools, such as electronic testers andimagers. A subset of promising candidates is advanced to the secondaryscreening stage, materials and process development stage 104.

Hundreds of materials (i.e., a magnitude smaller than the primary stage)may be evaluated during the materials and process development stage 104,which may focus on finding the best process for depositing each of thecandidate materials. A subset of promising candidates is selected toadvance to the tertiary screening stage, process integration stage 106.

Tens of material/process pairs may be evaluated during the processintegration stage 106, which may focus on integrating the selectedprocesses and materials with other processes and materials. A subset ofpromising candidates is selected to advance to device qualificationstage 108.

A few candidate combinations may be evaluated during the devicequalification stage 108, which may focus on the suitability of thecandidate combinations for high volume manufacturing. These evaluationsmay or may not be carries out on full-size substrates and productiontools. Successful candidate combinations proceed to pilot manufacturingstage 110.

The schematic diagram 100 is an example. The descriptions of the variousstages are arbitrary. In other embodiments of HPC, the stages mayoverlap, occur out of sequence, or be described or performed in otherways.

HPC techniques may arrive at a globally optimal process sequence byconsidering the interactions between the unit manufacturing processes,the process conditions, the process hardware details, and materialcharacteristics of components. Rather than only considering a series oflocal optima for each unit operation considered in isolation, thesemethods consider interaction effects between the multitude of processingoperations, influenced by the order in which they are performed, toderive a global optimum sequence order.

HPC may alternatively analyze a subset of the overall process sequenceused to manufacture a device; the combinatorial approach may optimizethe materials, unit processes, hardware details, and process sequenceused to build a specific portion of the device. Structures similar toparts of the subject device structures (e.g., electrodes, resistors,transistors, capacitors, waveguides, or reflectors) may be formed on theprocessed substrate as part of the evaluation.

While certain materials, unit processes, hardware details, or processsequences are varied, other parameters (e.g., composition or thicknessof the layers or structures, or the unit process action such ascleaning, surface preparation, deposition, surface treatment, or thelike) are kept substantially uniform across each discrete region of thesubstrate. Furthermore, while different materials or unit processes maybe used for corresponding layers or steps in the formation of astructure in different regions of the substrate, the application of eachlayer or the use of a given unit process may be substantially consistentamong the different regions. Thus, aspects of the processing may beuniform within a region (inter-region uniformity) or between regions(intra-region uniformity), as desired.

The result is a series of regions on the substrate that containstructures or unit process sequences that have been uniformly appliedwithin that region or, as applicable, across different regions. Thisprocess uniformity allows comparison of the properties within and acrossthe different regions so that the variations in test results are due tothe intentionally varied parameter (e.g., material, unit process, unitprocess parameter, hardware detail, or process sequence) and not a lackof process uniformity. The positions of the discrete regions can bedefined as needed, but are preferably systematized for ease of toolingand design of experiments. The number, location, and variants ofstructures in each region preferably enable valid statistical analysisof test results within and between regions.

FIG. 2 is a simplified schematic diagram illustrating a generalmethodology for combinatorial process sequence integration that includessite-isolated processing, conventional processing, or both. In oneembodiment, the substrate is initially processed using conventionalprocess N, then processed using site isolated process N+1. During siteisolated processing, an HPC module may be used, such as the HPC moduledescribed in U.S. Pat. No. 8,084,400. The substrate can then beprocessed using site isolated process N+2, and thereafter processedusing conventional process N+3. Testing is performed and the results areevaluated. The testing can include physical, chemical, acoustic,magnetic, electrical, optical, etc. tests. From this evaluation, aparticular process from the various site isolated processes (e.g. fromsteps N+1 and N+2) may be selected and fixed so that additionalcombinatorial process sequence integration may be performed using siteisolated processing for either process N or N+3. For example, a nextprocess sequence can include processing the substrate using siteisolated process N, conventional processing for processes N+1, N+2, andN+3, with testing performed thereafter.

Various other combinations of conventional and combinatorial processescan be included in the processing sequence. The combinatorial processsequence integration can be applied to any desired segments and/orportions of an overall process flow. Characterization can be performedafter each process operation and/or series of process operations withinthe process flow as desired. Furthermore, the flows can be applied toentire monolithic substrates, or portions such as coupons.

Parameters which can be varied between site-isolated regions include,but are not limited to, process material amounts, reactant species,process temperatures, process times, process pressures, process flowrates, process powers, reagent compositions, the rates at which thereactions are quenched, atmospheres in which the processes areconducted, order in which materials are deposited, hardware detailsincluding gas or liquid distribution assemblies, etc. These processparameter examples are not an exhaustive list; numerous other processparameters used in device manufacturing may also be varied.

Within a region, the process conditions may be kept substantiallyuniform, in contrast to gradient processing techniques which rely on theinherent non-uniformity of the material deposition. That is, eachsite-isolated region may be processed in a substantially consistent andsubstantially uniform way, even though the materials, processes, andprocess sequences may vary from region to region over the substrate.Thus, the testing will find optima without interference from processvariation differences between processes that are meant to be the same.Regions may be contiguous, or may overlap, or may be surrounded byunprocessed margins. Where regions are contiguous or overlapping, thematerials or process interactions in the overlap may be uncertain.However in some embodiments at least 50% of the area within a region isuniformly processed and all testing can be done in that uniform area.Experiments may be designed to allow potential overlap only betweenmaterials or processes that will not adversely affect the result of thetests.

Combinatorial processing can be used to determine optimal processingparameters (e.g., time, concentration, temperature, stirring rate, etc.)of wet processing techniques such as wet etching, wet cleaning, rinsing,and wet deposition techniques (e.g., electroplating, electrolessdeposition, chemical bath deposition, dip coating, spin coating, and thelike).

FIGS. 3A and 3B are two conceptual views of a combinatorially-processedsubstrate. FIG. 3A is a top view of substrate 300 showing 6site-isolated regions 302, 312, 322, 332, 342, and 352. Althoughsubstrate 300 is rectangular in the illustration, any suitable substrateshape such as circular, square, or polygonal may also be used in someembodiments. Although the site-isolated regions 302, 312, 322, 332, 342,and 352 are shown as separated from each other by unprocessed areas ofsubstrate 300, in some embodiments the site-isolated regions may becontiguous or partially overlapping. Some of the site-isolated regionsmay be chosen to be processed identically (as regions 302 and 352 areshown here with identical shading) to test the consistency of theresults on different regions of the same substrate.

FIG. 3B is a sectional view through section line A-A of FIG. 3A showingdifferent films formed on site-isolated regions 332, 342, and 352. Theregions could alternatively have identical (or no) films formed, and thevariation could instead be in the cleaning, etching, polishing, or someother treatment of the different regions.

FIG. 4 is a schematic diagram of one type of generic combinatorial wetprocessing system used to investigate processes involving liquids.Substrate 300 and site-isolated regions 332, 342, and 352 are shown incross-section similarly to FIG. 3B. Each site-isolated region is coveredby one of the individual reactor cells 402, 412, and 422. The reactorcells confine different liquids 406, 416, and 426 to their main cavities401, 411, and 421 and thus to the underlying regions 332, 342, and 352of the substrate. Conduits 404, 414, and 424 are connected to the cells.Some types of conduits deliver process liquid to the reactor cells,while other conduits may remove the process liquids, inject or removegases or buffer liquids, or maintain pressure equilibrium with thechamber ambient. The illustrated conduits 404, 414, and 424 are in fluidcommunication with main cavities 401, 411, and 421 of reactor cells 402,412, and 422 through ports 405, 415, and 425 respectively. Wet processessuch as cleaning, etching, surface treatment, surface functionalization,etc. may be investigated by HPC by varying liquid parameters (e.g.,composition, temperature, exposure time) between different site-isolatedregions.

FIGS. 5A, 5B, and 5C are various schematic views of an example of ano-contact reactor cell body. FIG. 5A is a bottom perspective view, FIG.5B is a top perspective view, and FIG. 5C is a cross-section throughsection A-A of FIG. 5B. A main cavity 501 is defined by an inner ceiling511 and an inner sidewall 521 extending to the cell bottom surface 533.A peripheral channel 502 extends around the periphery of main cavity 501between the inner sidewall 521 and the outer sidewall 523. Peripheralchannel 502 is also open at the cell bottom surface 533. At least oneperipheral port 512 extends between peripheral channel 502 and the outersurface of the cell body. At least four cavity ports 541, 551, 561, and571 extend between main cavity 501 and the outer surface of the cellbody. The outer surface of the cell body includes outer top 513 andouter sidewall 523.

Optionally, a spout 531 may extend into main cavity 501 to extend thesecond cavity port 551 that delivers liquid to main cavity 501. Spout531 may prevent incoming liquid from being drawn into any nearby gasexhausts operated through, for example, third cavity port 561. Forexample, a spout longer than 10 mm may effectively prevent liquid frombeing drawn into a nearby gas exhaust. Depending on its length, spout531 may also be used to withdraw a liquid from main cavity 501 ifcoupled to a pump by appropriate controllable valves. For example, thespout may extend to within 2 mm of the bottom surface. In someembodiments, an orifice 543 may be included on fourth cavity port 571 tocontrol inflow or outflow of gas to and from main cavity 501.

Numerous variations on the illustrated example are possible. Forexample, outer sidewall 523, inner sidewall 521, and peripheral channel502 need not have annular cross-sections parallel to cell bottom surface533. Rectangular, rounded-rectangular, polygonal, or ovoidcross-sections may be used. Peripheral port 512 and cavity ports 541,551, 561, and 571 need not penetrate through outer top 513 as shown, butmay alternatively penetrate through outer sidewall 523. The ports neednot be arranged in a straight line as illustrated, but may be arrangedin any convenient configuration. Peripheral channel 502 need not havethe same depth as main-cavity 501 as shown; either one may extendfurther into the cell body than the other.

FIGS. 6A and 6B are schematic cross-sections of a no-contact reactorcell with a controllable orifice processing an internal site and anexternal site of a substrate. In FIG. 6A, a reactor cell with an orifice643 processes an interior site on substrate 600. The reactor cell bottomsurface 633 does not touch the substrate 600, but hovers over it at agap height 610. Gap height 610 may be between about 0.2 mm and about 0.3mm. Gap height 610 may be controlled by a height (or proximity) sensor647 in communication with a controller 608, such as a computer. Heightsensor 647 may be on the reactor cell, or may be part of a substrateholder, or may be part of a machine vision system. Some embodiments ofmachine-vision-based height sensors may operate from outside thechamber, viewing the cells and substrates through windows.

The outer end of peripheral port 612 and the outer end of first cavityport 641 are connected to each other by gas conduit 604 to maintainpressure equilibrium between main cavity 601 and peripheral channel 602.A liquid source 605 is connected by liquid conduit 614 to second cavityport 651, delivering liquid 606 to the substrate through spout 631.Liquid delivery may also be controlled by controller 608. Gas is drawnout of main cavity 601 through the third cavity port 661, for example bya vacuum pump 615. The pressure inside main cavity 601 and peripheralchannel 602 is maintained slightly lower than ambient by a control loopincluding a pressure sensor 607, pressure monitor 617, orifice control612, and orifice valve 637. The control loop components 607, 617, 627,and 637, as well as vacuum pump 615, may also be controlled bycontroller 608.

Pressure sensor 607 measures the pressure inside the reactor cell or thepressure differential between the cell interior and the chamber ambient.Pressure monitor 617 monitors the pressure differential between the cellinterior and the chamber ambient. In some embodiments, pressure monitor617 monitors the signals from two or more pressure sensors, and one ofthe sensors may be in the chamber outside the reactor cell. If thepressure inside main cavity 601 drops below a predetermined minimumvalue, controller 608 causes orifice valve 637 to open, admittingambient gas from the surrounding chamber, and optionally may decrease orstop the pumping function a vacuum pump 615, until the pressure iswithin a desired range. If the pressure inside main cavity 601 risesabove a predetermined maximum value, controller 608 causes orifice valve637 to close, and optionally may increase the pumping function of vacuumpump 615, until the pressure is within a desired range.

The desired range and the minimum and maximum pressure values arecalculated to keep liquid 606 confined to main cavity 601 and peripheralchannel 602. Liquid 606 wets up the walls of main cavity 601 andperipheral channel 602, and is confined in gap 610 by meniscus 616. Thepressure range inside the cell within which this condition can bemaintained can be calculated from factors such as the viscosity ofliquid 606, the height of gap 610, and the adhesion of liquid 606 to thematerials of the top surface of substrate 600 and the walls of the maincavity and peripheral channel (for example, the hydrophilic orhydrophobic properties of those surfaces if a liquid 606 is an aqueoussolution). For example, for many process liquids 606, a pressure rangebetween −0.9 and −1.1″ (−23 to −28 mm) H₂O will confine the processliquid to the interior site.

In FIG. 6B, a reactor cell with an orifice 643 processes an exteriorsite on substrate 600. The reactor cell bottom surface 633 does nottouch the substrate 600, but hovers over it at a gap height 610. Gapheight 610 may be controlled by a height sensor 647 in communicationwith a controller 608.

In this configuration, peripheral port 612 is open to maintain pressureequilibrium between peripheral channel 602 and the chamber ambient.First cavity port 641 and second cavity port 651 are sealed, asschematically symbolized by stoppers 624. A gas source 625 is connectedby gas conduit 634 to third cavity port 661, delivering gas to the maincavity. The pressure inside main cavity 601 is maintained slightlyhigher than ambient by the control loop including pressure sensor 607,pressure monitor 617, orifice control 612, and orifice valve 637.Orifice valve 637 may be controllable to open and close, thus permittingor restricting gas flow between the main cavity and the chamber ambient.In some embodiments, valve 637 may be continuously variable between afull-open position and a fully-closed position. The control loopcomponents 607, 617, 627, and 637, as well as gas source 625, may alsobe controlled by controller 608.

If the pressure inside main cavity 601, as measured by pressure sensor607 and monitored by pressure monitor 617, drops below a predeterminedminimum value, controller 608 causes orifice valve 637 to close and gassource 625 to deliver more gas to raise the pressure to a value withinthe desired range. If the pressure inside main cavity 601 rises above apredetermined maximum value, controller 608 causes orifice valve 637 toopen, and optionally may decrease or stop delivery of gas from source625, until the pressure is within the desired range. The minimum andmaximum pressure values are calculated to keep liquid 626 excluded frommain cavity 601 and confined to peripheral channel 602 and an areaoutside the reactor cell. Liquid 626 wets up the walls of peripheralchannel 602 and the outer cell body wall 613, and is confined in gap 610by meniscus 636. The pressure range inside the cell within which thiscondition can be maintained can be calculated from factors such as theviscosity of liquid 626, the height of gap 610, and the adhesion ofliquid 626 to the materials of the top surface of substrate 600 and thewalls of the reactor cell (for example, the hydrophilic or hydrophobicproperties of those surfaces if a liquid 626 is an aqueous solution).For many process liquids 626, a pressure range between +0.9 and +1.1″(+23 to +28 mm) H₂O will confine the process liquid to the exteriorsite.

Processing the common exterior site of multiple reactor cells can beuseful in HPC to map, and remove from the individual SIR results, anyprocess non-uniformity varying spatially across the substrate due to thehardware or some underlying non-uniformity of the substrate itself.

FIGS. 7A and 7B are schematic cross-sections of a no-contact reactorcell with controllable gas inlet and exhaust processing an internal siteand an external site of a substrate. In FIG. 7A, a reactor cell with anorifice 733 processes an interior site on substrate 700. The reactorcell bottom surface 733 does not touch the substrate 700, but hoversover it at a gap height 710. Gap height 710 may be between about 0.2 mmand about 0.3 mm. Gap height 710 may be controlled by a height sensor747 in communication with a controller 708, such as a computer,similarly to the embodiment illustrated in FIG. 6A.

Peripheral port 712 and first cavity port 741 are connected to eachother by gas conduit 704 to maintain pressure equilibrium between maincavity 701 and peripheral channel 702. A liquid source 705 is connectedby liquid conduit 714 to second cavity port 751, delivering liquid 706to the substrate through spout 731. Liquid delivery may also becontrolled by controller 708. Gas is drawn out of main cavity 701through the fourth cavity port 771, for example by a vacuum pump 715.Gas from gas source 725 may be let into the main cavity through conduit734 and port 761. In some embodiments, the connections and roles of port761 and port 771 may be reversed. The pressure inside main cavity 701and peripheral channel 702 is maintained slightly lower than ambient bya control loop including a pressure sensor 707, pressure monitor 717,and flow control 757. Flow control 757 may be configured to control boththe inflow through port 761 and the outflow through port 771. Thecontrol loop components 707, 717, 757, 725, and 715 may also becontrolled by controller 708.

If the pressure inside main cavity 701, as measured by pressure sensor707 and monitored by pressure monitor 717, drops below a predeterminedminimum value, controller 708 causes more gas delivery from gas source725, and optionally may decrease or stop the pumping function a vacuumpump 715, until the pressure is within a desired range. If the pressureinside main cavity 701 rises above a predetermined maximum value,controller 708 increases the pumping function of vacuum pump 715, andoptionally may decrease or stop the gas delivery from gas source 725,until the pressure is within a desired range. As in FIG. 6A, the desiredrange and the minimum and maximum pressure values are calculated to keepliquid 706 confined to main cavity 701 and peripheral channel 702.Liquid 706 wets up the walls of main cavity 701 and peripheral channel702, and is confined in gap 710 by meniscus 716.

In FIG. 7B, a reactor cell with an orifice 733 processes an exteriorsite on substrate 700. The reactor cell bottom surface 733 does nottouch the substrate 700, but hovers over it at a gap height 710. Gapheight 710 may be controlled by a height sensor 747 in communicationwith a controller 708.

In this configuration, peripheral port 712 is open to maintain pressureequilibrium between peripheral channel 702 and the chamber ambient.First cavity port 741 and second cavity port 751 are sealed, asschematically symbolized by stoppers 724. Gas source 725 remainsconnected by gas conduit 734 to third cavity port 761 and vacuum pump715 remains connected to fourth cavity port 771. The pressure insidemain cavity 701 is maintained slightly higher than the chamber ambientby the control loop including pressure sensor 707, pressure monitor 717,and flow control 757 that may control both inflow through third cavityport 761 and outflow through fourth cavity port 771. The control loopcomponents may also be controlled by controller 708.

If the pressure inside main cavity 701, or the pressure differentialbetween main cavity 701 and the chamber ambient, drops below apredetermined minimum value, controller 708 causes more gas deliveryfrom gas source 725, and optionally may decrease or stop the pumpingfunction a vacuum pump 715, until the pressure is within a desiredrange. If the pressure inside main cavity 701 rises above apredetermined maximum value, controller 708 increases the pumpingfunction of vacuum pump 715, and optionally may decrease or stop the gasdelivery from gas source 725, until the pressure is within a desiredrange.

Thus the functions and connections of ports 761 and 771 are the samewhen processing an external site in FIG. 7B as when processing aninternal site in FIG. 7A; only the minimum, maximum, and desired rangeof differential pressures have changed to provide an overpressure in themain cavity instead of an underpressure. As in FIG. 6B, the minimum andmaximum pressure values are calculated to keep liquid 726 excluded frommain cavity 701 and confined to peripheral channel 702 and an areaoutside the reactor cell. Liquid 726 wets up the walls of peripheralchannel 702 and the outer cell body wall 713, and is confined in gap 710by meniscus 736.

The examples in FIGS. 6A-7B demonstrate that any suitable known methodof regulating pressure inside the reactor cell to be slightly under orslightly over chamber ambient can be used in some variant of this typeof reactor cell.

FIG. 8 is a flowchart of a method for processing an internal site on asubstrate. Initially, the connections to the cavity and peripheral portsare configured 801. A peripheral port is connected to a first cavityport, a liquid source is connected to a second cavity port, andconnections to a third cavity port and a fourth cavity port operate toprovide a slight gas underpressure compared to chamber ambient. If thefourth cavity port has an orifice with a controllable valve as in FIGS.6A and 6B, a vacuum pump may be connected to the third cavity port.Without a controllable orifice, a gas source may be connected to thethird cavity port and a vacuum pump may be connected to the fourthcavity port, or vice versa.

The reactor cell is positioned 802 over the substrate without touchingit, leaving a narrow gap (e.g., between about 0.2 mm and about 0.3 mm)between the top surface of the substrate and the bottom surface of thecell. A below-ambient pressure is created 803 in the main cavity bycontrolling the inflow and outflow of gas through the third and fourthcavity ports.

Process liquid is introduced 804 into the main cavity through the secondcavity port. The process liquid may be a deposition layer material, anetchant, a cleaning solution, a polishing mixture, or any other liquidused for any other process. Due to the underpressure, the process-liquidforms a meniscus in the gap and wets up the walls of the main cavity andthe peripheral channel above the cell bottom. The liquid may beintroduced 804 to a depth of, for example, between 4 mm and 10 mm.

As the liquid is introduced 804 and the substrate is processed 805, thepressure inside the main cavity is maintained within a desired rangebelow chamber ambient pressure by controlling the inflow and outflow ofgas through the third and fourth cavity ports. Keeping the pressurewithin the desired range confines the process liquid to an area of thesubstrate underneath this cell, within the outer periphery of aprojection of the peripheral channel onto the substrate surface. Forexample, the desired range may be between −23 mm and −28 mm H₂O.

When the process using the process liquid is complete, the processliquid is removed 806 from the substrate. This may be done in any mannerused for known substrate-contacting reactor cells; for example, bypumping it out of the cell through a liquid-exhaust conduit, or byraising the cell higher above the substrate and rinsing the entiresubstrate with a rinsing solution. In processes where it is criticalthat the process liquid must not touch any part of the substrate otherthan the interior site, the underpressure may be maintained while theliquid is pumped out to keep it confined to the interior site. If abrief contact with the process liquid would not adversely affect part ofthe substrate outside the interior site, the underpressure may bereleased while the liquid is being removed 806. Afterward, the nextprocess 809 may begin.

FIG. 9 is a flowchart of a method for processing an external site on asubstrate. Initially, the connections to the cavity and peripheral portsare configured 901. A peripheral port is opened to vent the peripheralchannel to the ambient atmosphere in the chamber, the first and secondcavity ports are sealed, and connections to a third cavity port and afourth cavity port operate to provide a slight gas overpressure comparedto chamber ambient. If the fourth cavity port has an orifice with acontrollable valve as in FIGS. 6A and 6B, a gas source may be connectedto the third cavity port. Without a controllable orifice, a gas sourcemay be connected to the third cavity port and a vacuum pump may beconnected to the fourth cavity port, or vice versa.

The reactor cell is positioned 902 over the substrate without touchingit, leaving a narrow gap (e.g., between about 0.2 mm and about 0.3 mm)between the top surface of the substrate and the bottom surface of thecell. An above-ambient pressure is created 903 in the main cavity bycontrolling the inflow and outflow of gas through the third and fourthcavity ports.

Process liquid is introduced 904 onto the substrate outside the maincavity. The process liquid may be a deposition layer material, anetchant, a cleaning solution, a polishing mixture, or any other liquidused for any other process. Due to the overpressure, the process-liquidforms a meniscus in the gap and wets up the walls of the peripheralchannel and the outer sidewall of the cell above the cell bottom. Theliquid may be introduced 904 to a depth of, for example, between 4 mmand 10 mm.

As the liquid is introduced 904 and the substrate is processed 905, thepressure inside the main cavity is maintained within a desired rangeabove chamber ambient pressure by controlling the inflow and outflow ofgas through the third and fourth cavity ports. Keeping the pressurewithin the desired range confines the process liquid to an area of thesubstrate outside the inner periphery of a projection of the peripheralchannel onto the substrate surface, and excludes the liquid from thearea under the main cavity. For example, the desired range may bebetween +23 mm and +28 mm H₂O.

When the process using the process liquid is complete, the processliquid is removed 906 from the substrate. This may be done in any mannerused for known substrate-contacting reactor cells. In processes where itis critical that the process liquid must not touch an inner part of aninterior site (i.e., the area under the main cavity), the overpressuremay be maintained while the liquid is removed so that no liquid flowsinto that area. If a brief contact with the process liquid would notadversely affect that area, the overpressure may be released while theliquid is being removed 906. Afterward, the next process 909 may begin.

FIGS. 10A-10D are conceptual views of substrates with sequentiallyprocessed internal and external sites. FIG. 10A is a top view of asection of a substrate 1000 where both an interior site and an exteriorsite have been processed using one of the described no-contact reactorcells. Circular area 1001 is the area that was located under the maincavity of the reactor cell. Annular area 1003 surrounding circular area1001 is the area that was located under the peripheral channel of thereactor cell. Rectangular area 1002 outside annular area 1003 is thearea that was located outside the outer boundary of the peripheralchannel.

As shown in FIGS. 6A-7B, both an interior site and an exterior site of areactor cell may include annular area 1003 under the peripheral channel,causing area 1003 to be processed twice. FIGS. 10B-10D are sectionalviews through section B-B of FIG. 10A, showing some of the possibleresults of the overlap of the two processed areas.

In FIG. 10B, sequential processes with a no-contact cell deposited newlayer 1010 on substrate 1000. A raised ring, appearing in the sectionalview as a pair of bumps 1003B, resulted from the double processing ofoverlap zone 1003.

In FIG. 10C, sequential processes with a no-contact cell etched uniformlayer 1020 on substrate 1000 down from its previous height 1004. Anindented ring, appearing in the sectional view as a pair of troughs1003C, resulted from the double processing of overlap zone 1003.

Often, in the HPC context, the doubly-processed overlap regions can beignored by doing all the characterizations in other parts of thesubstrate. However, there are situations where the overlap regions mayshare the characteristics of the non-overlap regions.

In FIG. 10D, sequential processes with a no-contact cell processed layer1030 on substrate 1000 without creating any non-uniformity in theoverlap zone. A number of approaches can produce this result. Forexample, a layer formed like 1010 with double deposition in the overlapzone might, in some circumstances, be etched like 1020 such that twoetch steps in the overlap zone level the raised area to the same planeas its surroundings. As another example, layer 1030 may have been buriedunder an overlayer 1040, which was wholly etched away using a wetetchant that does not etch layer 1030. The second exposure therefore didnot affect layer 1030. As a further example, layer 1030 could be acoating or other surface treatment that chemically reacts withunprocessed substrate 1000 but not with an already-reacted area 1001 or1002. Other processes can also result in a uniformly processed interiorsite and exterior site with no non-uniformity in the overlap zone.

Although the foregoing examples have been described in some detail toaid understanding, the invention is not limited to the details in thedescription and drawings. The examples are illustrative, notrestrictive. There are many alternative ways of implementing theinvention. Various aspects or components of the described embodimentsmay be used singly or in any combination. The scope is limited only bythe claims, which encompass numerous alternatives, modifications, andequivalents.

What is claimed is:
 1. A reactor cell, comprising: a cell body having anouter sidewall; a main cavity in the cell body; first, second, third,and fourth cavity ports extending from the main cavity to an outersurface of the cell body; a peripheral channel in the cell body; and aperipheral port extending from the peripheral channel to the outersurface of the cell body; wherein the main cavity and the peripheralchannel are open at a bottom surface of the cell; wherein an innersidewall surrounds the main cavity; and wherein the peripheral channelextends around the periphery of the main cavity between the innersidewall and the outer sidewall.
 2. The reactor cell of claim 1, furthercomprising a spout extending into the main cavity from the second cavityport.
 3. The reactor cell of claim 2, wherein the spout is longer thanabout 10 mm.
 4. The reactor cell of claim 2, wherein the spout extendsto within 2 mm of the bottom surface.
 5. The reactor cell of claim 1,wherein the outer sidewall, the inner sidewall, and the peripheralchannel have annular cross-sections parallel to the bottom surface. 6.The reactor cell of claim 1, wherein the outer sidewall, the innersidewall, and the peripheral channel have circular, rectangular,rounded-rectangular, ovoid, or polygonal cross-sections parallel to thebottom surface.
 7. The reactor cell of claim 1, wherein at least one ofthe first cavity port, the second cavity port, the third cavity port thefourth cavity port, or the peripheral port penetrates an outer top ofthe cell body.
 8. The reactor cell of claim 1, wherein the main cavityand the peripheral channel have equal depth.
 9. The reactor cell ofclaim 1, further comprising a height sensor configured to measure a gapheight of the bottom surface above a substrate.
 10. The reactor cell ofclaim 9, wherein the gap height is calculated to support a stablemeniscus of process liquid across the gap, given a viscosity for theprocess liquid and a pressure differential between the main cavity andan ambient atmosphere.
 11. The reactor cell of claim 9, wherein the gapheight is between about 0.2 mm and 0.3 mm.
 12. The reactor cell of claim1, further comprising a pressure sensor configured to measure a pressureinside the main cavity or a pressure differential between the maincavity and an ambient atmosphere outside the cell body.
 13. The reactorcell of claim 12, further comprising: a pressure monitor configured tomonitor the pressure differential between the main cavity and an ambientatmosphere outside the cell body; and a controller configured toregulate gas flow into and out of the main cavity to keep the pressuredifferential between a predetermined minimum value and a predeterminedmaximum value.
 14. The reactor cell of claim 1, further comprising: agas conduit connecting an outer end of the peripheral port to an outerend of the first cavity port; and a liquid source connected to deliverliquid to the main cavity through the second cavity port.
 15. Thereactor cell of claim 1, further comprising: a first seal preventing gasflow through the first cavity port between the main cavity and the outersurface of the cell body; and a second seal preventing gas flow throughthe second cavity port between the main cavity and the outer surface ofthe cell body.
 16. The reactor cell of claim 1, further comprising: anorifice on an outer end of the fourth cavity port; a controllableorifice valve connected to the orifice to permit or restrict gas flowbetween the main cavity and an ambient atmosphere; and a vacuum pumpconnected to the third cavity port; wherein the vacuum pump withdrawsgas from the main cavity, or the orifice valve admits ambient gas to themain cavity, as needed to maintain an underpressure in the main cavitycompared to the ambient pressure when a process liquid fills the cell toa height above a gap between the bottom surface of the cell and a topsurface of a substrate; and wherein the underpressure causes the processliquid to form a meniscus in the gap below an outer periphery of theperipheral channel.
 17. The reactor cell of claim 16, wherein theunderpressure is between about −23 and −28 mm H₂O.
 18. The reactor cellof claim 1, further comprising: an orifice on an outer end of the fourthcavity port; a controllable orifice valve connected to the orifice topermit or restrict gas flow between the main cavity and an ambientatmosphere; and a gas source connected to the third cavity port; whereinthe gas source delivers gas to the main cavity, or the orifice valveallows gas to leave the main cavity, as needed to maintain anoverpressure in the main cavity compared to the ambient pressure when aprocess liquid surrounds the cell to a height above a gap between thebottom surface of the cell and a top surface of a substrate; and whereinthe overpressure causes the process liquid to form a meniscus in the gapbelow an inner periphery of the peripheral channel.
 19. The reactor cellof claim 16, wherein the overpressure is between about +23 and +28 mmH₂O.
 20. The reactor cell of claim 1, further comprising: a gas sourceconnected to the third cavity port; and a vacuum pump connected to thefourth cavity port; wherein the gas source delivers gas to the maincavity, or the vacuum pump draws gas from the main cavity, as needed tomaintain a pressure differential between the main cavity and the ambientatmosphere when a process liquid is present inside or outside the cellto a height above a gap between the bottom surface of the cell and a topsurface of a substrate; wherein the pressure differential causes theprocess liquid to form a meniscus in the gap below a periphery of theperipheral channel; wherein the pressure differential is negative if theprocess liquid is inside the cell; and wherein the pressure differentialis positive if the process liquid is outside the cell.